Need help: wrong throwout bearing??

[CobraV8]

I have a close ratio toploader with lakewood bellhousing in my car and had a problem with the clutch being way to stiff right from the start. I've tried several sizes master and slave cylinders without any success, now I moved the pedal assembly up and installed longer pedals for better leverage and also changed to a clutch cable. But the clutch is still very hard to engage.

Someone told me that maybe the throwout bearing could be the wrong one for the pressure plate I use. It's a diaphragm type, and I was told I might need a throw out bearing with a rounded contact face for the pressure plate, otherwise reduced leverage will be the result.

The throw out bearing I installed has a flat face where it pushes on the clutch.

Could this cause such a severe increase in clutch force? I mean I'm only 25 and have no problems with my left leg, but the car is nearly undrivable because of the stiff clutch.

Simon